Experimental study on shear performance of dry-type vertical seam for modular hybrid wind turbine tower

Abstract:

The interface of dry-type vertical seam without grouting for prestressed concrete hybrid tower uses epoxy resin structural adhesive and bending bolts with pre-tension applied to resist shear. Compared with the traditional grouted wet connection with connecting steel bars, this approach can greatly improve on-site installation efficiency. Aiming at the shear performance of the vertical seam interface of dry-type connection, one direct shear static test and two direct shear fatigue tests were carried out on full-scale specimens. The failure mode, bond-slip curves, and bearing capacity calculation of the vertical seam interface under static shear loading were systematically investigated. Furthermore, the fatigue failure mode, degradation of shear stiffness, and methods for fatigue life prediction of the seam interface were further analyzed. The results of experimental research and theoretical analysis show that both static and fatigue tests of the dry-type vertical seams have brittle failure modes. The interface failures can be divided into two regions: interface debonding and delamination of the concrete protective layer—each occupying roughly 50% of the damaged area. The pre-tension applied by the bending bolts can effectively improve the shear capacity of the structural adhesive interface. The upper limit of load is the key factor affecting the shear fatigue performance of vertical seams, and the fatigue life is negatively correlated with the upper limit of load. The shear capacity of the vertical seam interface is provided jointly by the friction force generated by the direct shear of concrete and the pre-tension of the bending bolts. The calculation formula of the shear capacity of the vertical seam interface deduced by the superposition method shows high accuracy. The Fib Model Code specification formula is capable of predicting the shear fatigue life of vertical seams with commendable accuracy and a built-in safety margin, rendering it highly valuable for engineering applications.